The use of mobile telephones has become widespread throughout the world. One reason for the widespread use is the advent of cellular network communication standards such as GSM which enable a subscriber to “roam”, that is to operate the mobile telephone on networks in other regions and countries as well as on the subscriber's own home network.
When a subscriber makes a call while roaming, information relating to the call is passed from the service provider associated with the foreign network to the service provider of the home network. This information can then be used by the home service provider to generate the appropriate billing information. However as the format of information coming from the foreign service provider is different from that required by the home service provider a conversion of the information must take place at some point in the transfer process.
In existing systems the procedures governing the conversion of information have been “hard coded” into the application software. This has the disadvantage that any necessary change to the conversion process requires modification of the application software. Change might be required, for example, if a change in the data format occurs, or if a reciprocal agreement is arranged between the home service provider and a further foreign service provider.
Modification of the application software is an expensive and time consuming task. It would therefore be desirable to have a more flexible system which can be modified more readily as required.